It is known that a gas engine utilized in power generation equipment can attain a high power generation efficiency when its operation is continued under a situation in which knocking is not occurring but slight knocking might occur. On the other hand, since knocking with a high intensity causes damage to a cylinder, it is required that the knocking be prevented from occurring with greatest effort.
To this end, for example, Patent Literature 1 discloses a knocking control system for a gas engine for controlling occurrence of the knocking. This knocking control system is configured to change a fuel feed amount or an ignition timing of a corresponding cylinder to prevent occurrence of the knocking when a knocking occurrence ratio exceeds a predetermined threshold. This occurrence ratio is calculated at each passage of a predetermined number of cycles. A compensation value for changing the fuel feed amount or the ignition timing is decided at each passage of the predetermined number of cycles, according to a deviation between the occurrence ratio and a threshold. Especially when the knocking occurs frequently, the fuel feed amount is reduced to suppress occurrence of the knocking.